The present invention relates to a method and means for deicing aircraft.
The term "deicing of aircraft" refers to the process of snow and ice removal from the surface of aircraft on the ground. This process has always been a time-consuming and expensive job. Studies have shown that at least 75% of all deicing is done between the temperatures of 24.degree. and 38.degree. F. Under these atmospheric conditions, the humidity, wind, barometric pressure, and precipitation conditions may vary.
Under presently known methods, the deicing of aircraft is accomplished by spraying a mixture of "glycol" and water on the aircraft. The term "glycol" is used in the art for deicing fluid commonly made up of a mixture of ethylene glycol, propylene glycol and certain other additives such as corrosion inhibitor, a wetting agent, and glucose, which make the fluid adhere to the appropriate surfaces while the airplane taxies to the end of the runway. There are many different deicing fluids on the market, and they are referred to hereinafter by the term "glycol." A primary attribute of the "glycol" is its ability not to freeze and also its ability to leave a thin film on the airplane after the excess fluid has drained off.
In the past, deicing has been a single operation wherein a 50/50 mixture of glycol and water was applied to remove snow and ice and the residue film provided an anti-icing function. By "anti-icing" is meant the provision of a thin film of antifreeze-like substance which protects the wings and skin of the airplane against formation of additional ice thereon. In these prior methods of deicing, the glycol was traditionally mixed with water in a 50/50 ratio.
This prior procedure always left a coating of glycol on the wings which was not always desirable, and in fact many times was undesirable because the ambient temperature could be low enough that dry precipitation (such as dry snow) could be coming down which would not stick to a clean dry wing, but which would stick to the wet glycol covered wing. Therefore, this prior method often caused undesirable buildup of sticking snow on the wings after the deicing operation.
The present invention improves upon the prior methods for deicing airplanes by separating the deicing and the anti-icing operations into two separate operations. In the deicing operation, a water solution substantially free of glycol is heated to a temperature of from approximately 160.degree. F. to approximately 190.degree. F. Once the water is heated, it is sprayed on the skin of the airplane. The heat of the water warms the wings and causes the ice to break loose and be washed away by the stream of water. When atmospheric conditions are suitable for evaporation, the water will evaporate into the air, and in so doing causes cooling and drying of the aircraft skin. This results in a cold, dry skin which is not susceptible to accumulating cold precipitation.
After the airplane has been deiced, the captain of the airplane can determine whether or not anti-icing is necessary. If the weather includes wet precipitation falling, the captain may determine that further anti-icing measures should be taken. In this case a thin film of glycol is sprayed on the airplane so as to provide an anti-freezing film on the outer surface of the aircraft. However, if a dry snow is falling, or if no snow at all is falling, there is no need for any anti-icing solution to be sprayed on the airplane after the deicing operation.
In the past, glycol was plentiful and reasonably priced. Recently the price of glycol has increased many fold over its earlier price, largely due to the fact that glycol is from ethylene stock which is mainly a by-product of natural gas, but which also comes from crude oil. In the past it was considered a waste product and surplus. However, recently ethylene has been used in producing synthetic fibers, and accordingly, a shortage of ethylene has developed as the demand for synthetic fibers has grown. The result has been a shortage of glycol and a corresponding increase in price. The present invention minimizes the use of glycol and for that reason is advantageous.
The ideal condition for the airplane during winter precipitation is to have the airplane skin clean, dry, and cold. If there is snow under these conditions, the snow does not stick to the skin and merely blows off like dust with a little movement of the aircraft or with a light breeze. However, if the skin is wet there is a tendency for the blowing snow to stick to the aircraft skin and form ice thereon.
Another problem encountered with present methods is the polluting factor of the runoff of glycol from the airplane during the deicing operation. Previously this runoff was directed towards drains and into conventional sewage systems. Airports which are being planned, under construction or in use are being restricted from dumping this deicing fluid down the drains.
Therefore, a primary object of the present invention is the provision of a method for deicing airplanes which economically utilizes deicing fluid.
A further object of the present invention is the provision of a method for deicing an airplane wherein the skin of the airplane is either cooled and dried or heated in such a manner to prevent ice thereon before the airplane is cleared for takeoff.
A further object of the present invention is the provision of a method for deicing airplanes wherein the amount of glycol used for deicing and anti-icing the airplane is minimized.
A further object of the present invention is the provision of a method which minimizes or eliminates the need for heating glycol and consequently is safer.
A further object of the present invention is the provision of a method and means for deicing airplanes wherein little or no glycol is drained off to conventional drainage systems after the deicing operation is complete.
A further object of the present invention is the provision to separate the process into two phases, that of ice or snow removal (deicing) and that of anti-icing.
A further object of the present invention is the provision of a method which is economical, efficient, and simple to employ.